1. Field of the Invention
The present invention relates to a method and apparatus for the synthesis of vanadium oxide and, more particularly, to a method and apparatus for the continuous synthesis of vanadium oxide.
2. State of the Art
Various vanadium oxides are used as an active cathode material in primary and secondary batteries, particularly V.sub.6 O.sub.13 and V.sub.3 O.sub.8 (hereinafter referred to generally as vanadium oxide). Most known processes for the synthesis of vanadium oxide produce vanadium oxide in batch form. For example, one of the techniques for synthesis of vanadium oxide involves the decomposition of ammonium metavanadate NH.sub.4 VO.sub.3 at elevated temperatures in an inert atmosphere. Subsequent steps involve maintaining the material at elevated temperatures for between twelve and sixteen hours, and subsequently cooling the vanadium oxide to room temperature.
As another example, the article Large Scale Preparation of Non-Stoichiometric V.sub.6 O.sub.13, Pryor et al., Preprint from the 16th International Power Sources Symposium (1988), describes the synthesis of large (e.g. 500 grams) batches of vanadium oxide in a rotating drum that is sealed, purged with argon, heated to and maintained at 700.degree. K. for four hours, and then cooled to below 370.degree. K. before removing the product. According to the article, the primary objectives of the process were stoichiometric control and uniformity of product. According to the article, the important parameters in achieving the objectives were: 1) uniform heating and good temperature control: 2) even exposure of the material to evolved NH.sub.3 ; 3) control of the rate of NF.sub.3 removal: and 4) total exclusion of air.
The above-described process has, however, various shortcomings. For instance, the process requires relatively long periods for preparation of a batch. Further, because the process is a batch process, there are inherent risks. For example, if a batch is bad, then other production steps depending upon production of the batch are delayed. Further, batch processes are typically characterized by the need for workers to handle trays containing ammonium metavanadate or vanadium oxide, both of which are toxic, while transporting material to and from processing apparatus.